Supporters of six Saudi reformists arrested this month said on Wednesday they had failed to secure their release after talks with the kingdom's powerful interior minister.
About a dozen pro-reform activists met Prince Nayif late on Monday but the discussions revealed deep differences between authorities and campaigners, liberal university professor Khalid al-Dakhil said.
"The discussion went very well but on the other hand it was clear there is a gulf of misunderstanding between the reformers and the government," he said.
They were among 13 reformists arrested last week by the authorities for calling for the absolute monarchy to move towards a more constitutional model and urging the royal family to set a timetable for political change.
Their detention overshadowed a visit by US Secretary of State Colin Powell, who said his country was troubled by the restrictions on free speech demonstrated by the arrests.
Seven detainees have been released but Saudi Arabia told Powell that the others could face charges, US officials said.
The United States is eager to promote reform in the Middle East and has encouraged its long-standing ally, the world's biggest oil producer, to speed up change since the September 11, 2001, attacks.
Dakhil said Prince Nayif warned the reformers against trying to "take advantage of external circumstances" by coordinating their demands with international pressure.
"That is part of the misunderstanding," he said. "Nobody wants any intervention from the outside, neither from Europe but especially not from the United States."
Dakhil said the prince wanted the remaining detainees to pledge to stop issuing statements calling for reform, but said he had not explicitly made that a condition for their release.
"The discussion went very well but on the other hand it was clear there is a gulf of misunderstanding between the reformers and the government"
More than 130 people signed a petition earlier this week calling for the immediate release of the "prisoners of conscience" and the speeding up of reforms "to protect the nation from dire dangers that surround her".
Ten of the signatories later withdrew their backing, saying they did not want to jeopardise talks with the government.
Washington believes lack of democracy in Arab states has helped fuel "militancy" and plans to unveil a Greater Middle East Initiative for reforms in June.
Saudi Arabia says it will not allow its cautious programme of political change to be influenced by outside pressure. It rejected US criticism of the arrests, saying they were an internal affair.